In the LTE Release8/9, in order to measure the channel quality and demodulate the received data symbols, a Common Reference Signal (CRC) is designed, so that the User Equipment (UE) can measure the channel through the CRC, thus deciding that the UE reselects the cell and hands over to a target cell, and measures the channel quality when the UE is in a connected state, and when the interference level is higher, the physical layer can disconnect the connection through high-layer related wireless link connection failure signaling. In the LTE R10, in order to further enhance the average spectrum utilization rate of the cell and the spectrum utilization rate of the cell border and the throughput of various UEs, two reference signals are defined respectively, i.e., Channel Statement Information Reference Signal (CSI-RS) and Demodulation Reference Signal (DMRS), wherein, the CSI-RS is used for the measurement of the channel, and the Precoding Matrix Indicator (PMI), Channel Quality Indicator (CQI) and Rank Indicator (RI) required to be fed back to the eNB by the UE can be calculated through the measurement of the CSI-RS. For the demodulation of the downlink shared channel, the DMRS demodulation can be used to reduce interference between different receiving sides and various cells with a beam method, and can reduce the performance reduction caused by the codebook granularity, and reduce the overhead of the downlink control signaling to some extent (since the bit overhead of the PMI needs not to be added on the physical downlink control channel).
In the LTE R8, R9 and R10, the physical downlink control channels are primarily distributed on first 1 or 2 or 3 Orthogonal Frequency Division Multiplexing (OFDM) symbols of one subframe, and the specific distribution needs to be configured according to different subframe types and the number of CRS ports, as illustrated in Table 1.
The Physical Downlink Control Channel (PDCCH) refers to the downlink control channel of R8/R9/R10.
TABLE 1The number of OFDM symbols for PDCCHNumber of OFDMNumber of OFDMsymbols of the PDCCHsymbols of the PDCCHSubframeswith NRBDL >10with NRBDL ≦10subframes 1 and 6 of subframe type 21, 22the MBSFN subframe on the carrier supporting1, 22PDSCH, and the CRS is configured with 1 or 2portsthe MBSFN subframe on the carrier supporting22PDSCH, and the CRS is configured with 4 portsthe subframe on the transmission carrier not00supporting PDSCHthe non-MBSFN subframe configured as PRS1, 2, 32, 3(except for the subframe 6 of the frame structuretype 2)all other cases1, 2, 32, 3, 4
Each receiving side needs to perform a blind detection on the first three symbols, and the initial location of the blind detection and the number of elements of the control channels are related to the temporary identities of the wireless network allocated to the receiving side and different control information. Generally, the control information can be divided into public control information and dedicated control information, and the public control information is generally located in a public search space of the physical downlink control channel, and the dedicated control can be located in all public spaces and the dedicated search space. After the receiving side performs the blind detection, it determines whether the current subframe comprises the public system message, the downlink or the uplink scheduling information. As such downlink control information does not comprise the HARQ feedback, it needs to ensure that the detected bit error rate is as low as possible.
In the LTE R10 heterogeneous network, as different base station types have strong interference, in consideration of the problem of interference with the Pico from the Macro eNodeB and the problem of interference with the Macro eNodeB from the Home eNodeB, a method of using the resource muting is provided to solve the problem of interference between different types of base stations, and the specific resource muting methods can be divided into muting methods based on subframes, for example, the ABS method, and methods based on resource elements, for example, the CRS muting method.
The above method not only increases the waste of resources, but also brings large limitation on the scheduling, especially when considering the ABS configuration of the Macro eNodeB, if the more the Picos which are distributed are, the more the ABSs configured by the Macro eNodeB are, thus bringing large influence on the Macro eNodeB, which will increase the waste of resources while increasing the delay of the scheduling. While for the control channel, the interference of the data resources of different control channels can be reduced under the ABS, but the problem of interference of CRS resources and data resources can not be solved, while for the muting CRS method, the interference between data resources can not be solved, and the backward compatibility of this method is not good, which increases the accessing time delay while possibly requires more standardized efforts.
In the LTE R11 phase, more users may be introduced to transmit on the MBSFN subframes, thus resulting in insufficiency of the capacity of the PDCCH which can be carried by the 2 OFDM symbols configured by the MBSFN, and in order to ensure the backward compatibility with the R8/R9/R10 users, it needs to evolve new resources for transmitting control information on the PDSCH resources (ePDCCH for short hereinafter), and COMP technology is introduced in the R11 phase, which can solve the problem of interference between different types of cells by means of spatial division, and save the overhead of the resources, avoid the waste of resources due to the muting, and reduce the limitation on the scheduling. However, it can not solve the problem by the spatial division method according to the current time-domain PDCCH manner, and in consideration of the backward compatibility with the R8 and R9, the control channel manner of the time-domain PDCCH must be reserved, and at this time, how to use the spatial division technology to solve the interference between the control channels needs to introduce a new control channel, i.e., Enhanced Physical Downlink Control Channel (ePDCCH). The ePDCCH can achieve good effect of the spatial division, reduce the interference between the physical downlink control signaling of different nodes, and enhance the capacity of the PDCCH of the system.
Another problem discussed for the R11 phase is the problem of insufficiency of resources of the Physical Hybrid ARQ Indicator Channel (PHICH). Since it needs to consider the support for more uplink users with respect to the R11 especially in the scene 4, the number of supportable uplink users increases obviously, the capacity of the PHICH will be limited greatly, and in the R11 discussion process, different terminals are supported to have the same uplink time-frequency resources/cyclic shift allocation/CSHopping allocation/different reference signal sequences, at this time, the traditional PHICH detection resources allocation is not applicable, and it needs to further enhance the PHICH, and thus, it is necessary to further do research into the technology for enhancing the PHICH, and such enhanced PHICH is commonly referred to as an Enhanced Physical Hybrid ARQ Indicator Channel (ePHICH).
In the current R11 conference discussion phase, another problem discussed is a problem of whether it needs to enhance the control signaling of the public search space, and that problem mainly considers whether the capacity of the current R10 public search space is limited, and the problem of interference between different nodes, especially the interference with the Pico from the Macro, and if the capacity is limited and the problem of interference is severe, it is necessary to introduce an enhanced public search space. Since the interference avoidance of the time-frequency resource locations can be performed in the PDSCH region, the enhanced public search space based on the PDSCH region is a current hot point, and such enhanced public search space based on the PDSCH region is commonly referred to as an Enhanced Common Search Space (eCSS).